Organic electroluminescent materials and devices

ABSTRACT

This invention discloses iridium complexes containing phenylpyridine ligand wherein there is an aryl or heterocyclic ring fused into phenyl ring. This invention also discloses organic light emitting devices comprising an anode, a cathode, and an organic layer disposed between the anode and the cathode, the organic layer comprising an iridium complex, and formulations comprising iridium complexes. The iridium complexes showed desired device performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 62/077,469, filed Nov. 10, 2014, the entirecontents of which is incorporated herein by reference.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to compounds for use as emitters anddevices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

When the aryl or heteroaryl ring in the ligands of metal complexes isnot fused with a five-membered saturated carbon ring, the molecule maybe less rigid, thereby reducing molecular stability, decreasing complexdevice lifetime and diminishing color purity. There is a need in the artfor novel compounds with improved stability and enhanced properties. Thepresent invention addresses this unmet need.

SUMMARY OF THE INVENTION

According to an embodiment, a compound is provided comprising a ligandL_(A) of Formula I:

wherein R has the following structure and is fused to ring A:

wherein each Z¹ to Z⁸ is nitrogen or carbon;wherein the wave lines indicate the bonds to two of the adjacent Z¹ toZ⁴ of ring A;wherein when two of the adjacent Z¹ to Z⁴ are used to fuse to R, thosetwo of the adjacent Z¹ to Z⁴ are carbon;wherein R¹ and R⁴ each independently represent mono, di, tri, or tetrasubstitutions, or no substitution;wherein R² and R³ each independently represent mono, or disubstitutions, or no substitution;wherein X is O or S;wherein R¹, R², R³, R⁴, R⁵, and R⁶ are each independently selected fromthe group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof;wherein any two adjacent substituents are optionally joined to form aring, which can be further substituted;wherein the ligand L_(A) is coordinated to a metal M; andwherein the ligand L_(A) is optionally linked with other ligands tocomprise a tridentate, tetradentate, pentadentate or hexadentate ligand.

In one embodiment, M is selected from the group consisting of Ir, Rh,Re, Ru, Os, Pt, Au, and Cu.

In one embodiment, M is Ir.

In one embodiment, the ligand L_(A) is selected from the groupconsisting of:

In one embodiment each of Z¹ to Z⁴ is carbon. In another embodiment eachof Z⁵ to Z⁸ is carbon. In another embodiment each of Z¹ to Z⁸ is carbon.In yet another embodiment, at least one of Z⁵ to Z⁸ is nitrogen.

In one embodiment X is O.

In one embodiment R⁵ and R⁶ are each independently selected from thegroup consisting of hydrogen, deuterium, alkyl, cycloalkyl, aryl,heteroaryl, and combinations thereof. In another embodiment, R⁵ and R⁶are joined to form a ring.

In one embodiment, the ligand L_(A) is selected from the groupconsisting of compounds L_(A1) to L_(A508).

In another embodiment, the compound has the formula (L_(A))Ir(L_(B))₂ ofFormula II, having the structure:

wherein R⁷ and R⁸ each independently represent mono, di, tri, or tetrasubstitutions, or no substitution;wherein R⁷ and R⁸ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof and wherein any twoadjacent R⁷ and R⁸ are optionally joined to form a ring, which can befurther substituted.

In one embodiment L_(B) is selected from the group consisting of L_(B1)to L_(B225).

In one embodiment, the compound is selected from the group consisting ofcompound 1 through Compound 114,300; where each compound x has theformula Ir(L_(Ai))(L_(Bj))₂; wherein x=508j+i−508, i is an integer from1 to 508, and j is an integer from 1 to 225; wherein L_(Ai) is one ofL_(A1) to L_(A508) and L_(Bj) is one of L_(B1) to L_(B225).

According to another embodiment, an organic light emitting device (OLED)is provided. The OLED comprises an anode; a cathode; and an organiclayer, disposed between the anode and the cathode, comprising a compoundcomprising a ligand L_(A) of Formula I.

In one aspect, the OLED is incorporated into a device selected from thegroup consisting of a consumer product, an electronic component module,and a lighting panel.

In one embodiment, the organic layer comprises a host; wherein the hostcomprises a triphenylene containing benzo-fused thiophene or benzo-fusedfuran;

wherein any substituent in the host is an unfused substituentindependently selected from the group consisting of C_(n)H_(2n+1),OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1), Ar₁, Ar₁—Ar₂, C_(n)H_(2n)—Ar₁, orno substitution;

wherein n is from 1 to 10; and

wherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof.

In another embodiment, the organic layer further comprises a host,wherein the host comprises at least one chemical group selected from thegroup consisting of triphenylene, carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

In yet another embodiment, the organic layer layer further comprises ahost and the host is selected from the group consisting of:

and combinations thereof.

In one embodiment, the organic layer further comprises a host and thehost comprises a metal complex.

According to another embodiment, the invention provides a formulationcomprising a compound comprising a ligand L_(A) of Formula I:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 which is incorporated by reference inits entirety.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 which is incorporated byreference in its entirety.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. Such consumer products would include anykind of products that include one or more light source(s) and/or one ormore of some type of visual displays. Some examples of such consumerproducts include flat panel displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads-up displays, fully or partiallytransparent displays, flexible displays, laser printers, telephones,cell phones, tablets, phablets, personal digital assistants (PDAs),laptop computers, digital cameras, camcorders, viewfinders,micro-displays, 3-D displays, vehicles, a large area wall, theater orstadium screen, or a sign. Various control mechanisms may be used tocontrol devices fabricated in accordance with the present invention,including passive matrix and active matrix. Many of the devices areintended for use in a temperature range comfortable to humans, such as18 degrees C. to 30 degrees C., and more preferably at room temperature(20-25 degrees C.), but could be used outside this temperature range,for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo,” “halogen,” or “halide” as used herein includesfluorine, chlorine, bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branchedchain alkyl radicals. Preferred alkyl groups are those containing fromone to fifteen carbon atoms and includes methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, and the like. Additionally, thealkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms andincludes cyclopropyl, cyclopentyl, cyclohexyl, and the like.Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight andbranched chain alkene radicals. Preferred alkenyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkenyl groupmay be optionally substituted.

The term “alkynyl” as used herein contemplates both straight andbranched chain alkyne radicals. Preferred alkynyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkynyl groupmay be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are usedinterchangeably and contemplate an alkyl group that has as a substituentan aromatic group. Additionally, the aralkyl group may be optionallysubstituted.

The term “heterocyclic group” as used herein contemplates aromatic andnon-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also meansheteroaryl. Preferred hetero-non-aromatic cyclic groups are thosecontaining 3 or 7 ring atoms which includes at least one hetero atom,and includes cyclic amines such as morpholino, piperdino, pyrrolidino,and the like, and cyclic ethers, such as tetrahydrofuran,tetrahydropyran, and the like. Additionally, the heterocyclic group maybe optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplatessingle-ring groups and polycyclic ring systems. The polycyclic rings mayhave two or more rings in which two carbons are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings isaromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl,heterocycles, and/or heteroaryls. Additionally, the aryl group may beoptionally substituted.

The term “heteroaryl” as used herein contemplates single-ringhetero-aromatic groups that may include from one to three heteroatoms,for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole,triazole, pyrazole, pyridine, pyrazine and pyrimidine, and the like. Theterm heteroaryl also includes polycyclic hetero-aromatic systems havingtwo or more rings in which two atoms are common to two adjoining rings(the rings are “fused”) wherein at least one of the rings is aheteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls,aryl, heterocycles, and/or heteroaryls. Additionally, the heteroarylgroup may be optionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroaryl may be optionally substituted with one or moresubstituents selected from the group consisting of hydrogen, deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R′ is mono-substituted, then one R′ must be other than H.Similarly, where R′ is di-substituted, then two of R′ must be other thanH Similarly, where R′ is unsubstituted, R′ is hydrogen for all availablepositions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

When an aryl or heteroaryl ring in the ligands of metal complexes isfused with a five-membered saturated carbon group the complex devicelifetime can be enhanced and color purity potentially can be improvedcompared with devices that include the previously synthesized similarcomplexes in which the aryl or heteroaryl ring is not fused. Althoughnot wishing to be bound by any particular theory, this effect isbelieved to be due to the ring fusion making the molecule more rigid andtherefore potentially increasing the molecule's stability in general. Inaddition, molecular rigidification can make photoluminescent spectrumnarrower and better color CIE which are desired properties of OLED.Therefore, the present invention is based, in part, on the discoverythat fusing the ligands of metal complexes with five-membered saturatedcarbon groups provides a device with enhanced lifetime and improvedcolor purity.

Compounds of the Invention:

The compounds of the present invention may be synthesized usingtechniques well-known in the art of organic synthesis. The startingmaterials and intermediates required for the synthesis may be obtainedfrom commercial sources or synthesized according to methods known tothose skilled in the art.

In one aspect, the compound of the invention is a compound comprising aligand L_(A) of Formula I:

wherein R has the following structure and is fused to ring A:

wherein each Z¹ to Z⁸ is nitrogen or carbon;

wherein the wave lines indicate the bonds to two of the adjacent Z¹ toZ⁴ of ring A;

wherein when two of the adjacent Z¹ to Z⁴ are used to fuse to R, thosetwo of the adjacent Z¹ to Z⁴ are carbon;

wherein R¹ and R⁴ each independently represent mono, di, tri, or tetrasubstitutions, or no substitution;

wherein R² and R³ each independently represent mono, or disubstitutions, or no substitution;

wherein X is O or S;

wherein R¹, R², R³, R⁴, R⁵, and R⁶ are each independently selected fromthe group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof;

wherein any two adjacent substituents are optionally joined to form aring, which can be further substituted;

wherein the ligand L_(A) is coordinated to a metal M; and

wherein the ligand L_(A) is optionally linked with other ligands tocomprise a tridentate, tetradentate, pentadentate or hexadentate ligand.

The metal M is not particularly limited. Examples of metals useful inthe compounds of the present invention include, but are not limited to,transition metals such as Ir, Pt, Au, Re, Ru, W, Rh, Ru, Os, Pd, Ag, Cu,Co, Zn, Ni, Pb, Al, and Ga. In one embodiment, M is selected from thegroup consisting of Ir, Rh, Re, Ru, Os, Pt, Au, and Cu. In oneembodiment, M is Ir.

In one embodiment, the ligand L_(A) is selected from the groupconsisting of:

In one embodiment each of Z¹ to Z⁴ is carbon. In another embodiment eachof Z⁵ to Z⁸ is carbon. In another embodiment each of Z¹ to Z⁸ is carbon.In yet another embodiment, at least one of Z⁵ to Z⁸ is nitrogen.

In one embodiment X is O. In another embodiment, X is S.

In one embodiment R⁵ and R⁶ are each independently selected from thegroup consisting of hydrogen, deuterium, alkyl, cycloalkyl, aryl,heteroaryl, and combinations thereof. In another embodiment, R⁵ and R⁶are joined to form a ring.

In one embodiment, the ligand L_(A) is selected from the groupconsisting of compounds L_(A1) to L_(A508):

In one embodiment, the compound of the invention has the formula(L_(A))Ir(L_(B))₂ of Formula II, having the structure:

wherein R⁷ and R⁸ each independently represent mono, di, tri, or tetrasubstitutions, or no substitution;

wherein R⁷ and R⁸ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any two adjacent R⁷ and R⁸ are optionally joined to form a ring,which can be further substituted.

In one embodiment L_(B) is selected from the group consisting of L_(B1)to L_(B225):

In one embodiment, the compound is selected from the group consisting ofCompound 1 through Compound 114,300; where each compound x has theformula Ir(L_(Ai))(L_(Bj))₂; wherein x=508j+i−508, i is an integer from1 to 508, and j is an integer from 1 to 225; wherein L_(Ai) is one ofL_(A1) to L_(A508) and L_(Bj) is one of L_(B1) to L_(B225). For example,if the compound has formula Ir(L_(A35))(L_(B15))₂, the compound isCompound 7,147. In one embodiment, ligand L_(Ai) is at least one ligandL_(A). In one embodiment, ligand L_(Bj) is at least one ligand L_(B).

In some embodiments, the compound can be an emissive dopant. In someembodiments, the compound can produce emissions via phosphorescence,fluorescence, thermally activated delayed fluorescence, i.e., TADF (alsoreferred to as E-type delayed fluorescence), triplet-tripletannihilation, or combinations of these processes.

Devices:

According to another aspect of the present disclosure, an organic lightemitting device (OLED) is also provided. The OLED includes an anode, acathode, and an organic layer disposed between the anode and thecathode. The organic layer may include a host and a phosphorescentdopant. The emissive layer can include a compound according to FormulaI, and its variations as described herein.

The OLED can be one or more of a consumer product, an electroniccomponent module, an organic light-emitting device and a lighting panel.The organic layer can be an emissive layer and the compound can be anemissive dopant in some embodiments, while the compound can be anon-emissive dopant in other embodiments. The organic layer can be acharge transporting layer and the compound can be a charge transportingmaterial in the organic layer in some embodiments. The organic layer canbe a blocking layer and the compound can be a blocking material in theorganic layer in some embodiments.

In one embodiment, the OLED is incorporated into a device selected fromthe group consisting of a consumer product, an electronic componentmodule, and a lighting panel.

The organic layer can also include a host. In some embodiments, the hostcan include a metal complex. In one embodiment, the organic layercomprises a host; wherein the host comprises a triphenylene containingbenzo-fused thiophene or benzo-fused furan;

wherein any substituent in the host is an unfused substituentindependently selected from the group consisting of C_(n)H_(2n+1),OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1), Ar₁, Ar₁—Ar₂, C_(n)H_(2n)—Ar₁, orno substitution;

wherein n is from 1 to 10; and

wherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof.

In another embodiment, the organic layer further comprises a host,wherein the host comprises at least one chemical group selected from thegroup consisting of triphenylene, carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. Thehost can include a metal complex.

In another embodiment, the organic layer further comprises a host andthe host is selected from the group consisting of:

and combinations thereof.

In one embodiment, the OLED organic layer further comprises a host andthe host comprises a metal complex.

Formulations:

In yet another aspect of the present disclosure, a formulation thatcomprises a compound according to Formula I is described. Theformulation can include one or more components selected from the groupconsisting of a solvent, a host, a hole injection material, holetransport material, and an electron transport layer material, disclosedherein.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but are not limited to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, andcross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butare not limited to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, and azulene; the group consistingof aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each Ar isfurther substituted by a substituent selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are notlimited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹—Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹—Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹—Y¹⁰²) is a carbene ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁺/Fc couple lessthan about 0.6 V.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. While the Table below categorizes host materials as preferredfor devices that emit various colors, any host material may be used withany dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³—Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³—Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting of aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; thegroup consisting of aromatic heterocyclic compounds such asdibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene,benzofuran, benzothiophene, benzoselenophene, carbazole,indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole,triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole,thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine,oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole,indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline,isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine,phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine,phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each groupis further substituted by a substituent selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof.

In one aspect, the host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, when it is aryl or heteroaryl, ithas the similar definition as Ar's mentioned above. k is an integer from0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ isselected from C (including CH) or N.Z¹⁰¹ and Z¹⁰² is selected from NR¹⁰¹, O, or S.HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, the compound used in the HBL contains the same moleculeor the same functional groups used as the host described above.

In another aspect, the compound used in the HBL contains at least one ofthe following groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, the compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but is notlimited to, the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table Abelow. Table A lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

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  and  

 

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EXPERIMENTAL EXAMPLES Example 1 Device Examples

All example devices were fabricated by high vacuum (<10⁻⁷ Torr) thermalevaporation. The anode electrode is 800 Å of indium tin oxide (ITO). Thecathode consisted of 10 Å of LiF followed by 1,000 Å of Al. All devicesare encapsulated with a glass lid sealed with an epoxy resin in anitrogen glove box (<1 ppm of H₂O and O₂) immediately after fabrication,and a moisture getter was incorporated inside the package. The organicstack of the device examples consisted of sequentially, from the ITOsurface, 100 Å of LG101 as the hole injection layer (HIL), 450 Å ofCompound D as the hole transporting layer (HTL), 400 Å of Compound 1doped in Compound B as host with 10 or 15 weight percent of the iridiumphosphorescent compound as the emissive layer (EML), 50 Å of Compound Cas a blocking layer (BL), 450 Å of Alq (tris-8-hydroxyquinolinealuminum) as the ETL. The comparative Example with Compound A wasfabricated similarly to the Device Examples. The device results and dataare summarized in Tables 1 and 2. As used herein, Alq, Compound A, B, Cand D have the following structures:

TABLE 1 Device Structures of Inventive Compound and Comparative CompoundEML (400 Å, Example HIL HTL doping %) BL ETL Comparative LG101 Com- Com-Com- Com- Alq Example 1 100 Å pound D pound pound A pound C 450 Å 450 ÅB as host 10% 50 Å Comparative LG101 Com- Com- Com- Com- Alq Example 2100 Å pound D pound pound A pound C 450 Å 450 Å B as host 15% 50 ÅInventive LG101 Com- Com- Com- Com- Alq Example 1 100 Å pound D poundpound 1 pound C 450 Å 450 Å B as host 10% 50 Å Inventive LG101 Com- Com-Com- Com- Alq Example 2 100 Å pound D pound pound 1 pound C 450 Å 450 ÅB as host 15% 50 Å

TABLE 2 VTE Device Results λmax FWHM LT_(95%) (h) x y (nm) (nm) At 40mA/cm2 Comparative example 1 0.335 0.633 528 58 18 Comparative example 20.340 0.630 530 59 9 Inventive example 1 0.344 0.626 530 58 32 Inventiveexample 2 0.347 0.626 530 58 24

Table 2 is the summary of EL of comparative and inventive devices at1000 nits and life test at 40 mA/cm². The LT₉₅% of Comparative exampleCompound A at dopant concentration 10% and 15% are 18 and 9 hours vs 32and 24 hours for inventive example Compound 1, respectively. The devicelifetime results demonstrated that a fused ring and rigidification ofmolecules can result in better device performance in term of lifetime,which is a desired property for OLED devices.

Example 2 Synthesis of Compound 1 Synthesis of methyl2-(dibenzo[b,d]furan-4-yl)benzoate

To a 500 mL round bottom flask, methyl-2-bromobenzoate (15 g, 69.8mmol), dibenzo[b,d]furan-4-ylboronic acid (16.27 g, 77 mmol), Pd(PPh₃)₄(0.806 g, 0.698 mmol), K₂CO₃ (19.28 g 140 mmol) and 250 mL THF wereadded and nitrogen was bubbled through the reaction mixture for 30 mins.The reaction mixture was heated up to reflux and stirred at refluxovernight. The reaction mixture was cooled down and purified using asilica gel column with DCM 50% in heptane as elutant and about 8 grams(38% yield) of pure product was obtained.

Synthesis of 2-(2-dibenzo[b,d]furan-4-yl)phenylpropan-2-ol

Methyl 2-(dibenzo[b,d]furan-4-yl)benzoate (7.7 g, 25.5 mmol) wasdissolved in ˜150 mL anhydrous THF and cooled down to 0° C. To thesolution, ˜25.5 mL of a 3 M methyl magnesium bromide diether solutionwas added slowly and the reaction mixture was stirred overnight. Thereaction mixture was quenched with NH₄Cl aqueous solution and extractedwith DCM and dried over Na₂SO₄. ˜8 gram product was obtained afterevaporation of DCM. The product, which was confirmed by GC, was used forthe next step without further purification.

Synthesis of 7,7-dimethyl-7H-fluoreno[4,3-b]benzofuran

2-(2-dibenzo[b,d]furan-4-yl)phenylpropan-2-ol (8.0 g, 26.5 mmol) wasdissolved in 150 mL DCM and cooled down to 0° C. To the solution, 10 mLof a BF₃ (46.5%) ether complex solution was added slowly, then thereaction mixture was stirred overnight. Saturated NaHCO₃ aqueoussolution was slowly added while stirring until the formation of bubblesstopped. The reaction mixture was purified using a silica column with15% DCM in heptane as eluant. ˜4 g product was obtained after column.The product was confirmed by proton NMR and GC.

Synthesis of2-(7,7-dimethyl-7H-fluoreno[4,3-b]benzofuran-1-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

7,7-dimethyl-7H-fluoreno[4,3-b]benzofuran (4.0 g, 14.07 mmol) wasdissolved in anhydrous THF and cooled down to −78° C. 30 mL of 1.4 MSec-BuLi in cyclohexane was added into the solution once, and thereaction mixture was stirred for two hours at −78° C. 11.5 mL2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was added and thereaction mixture was stirred overnight. The reaction mixture wasquenched with NH₄OH aqueous solution and purified using a silica gelcolumn to yield ˜2.1 g (36.5% yield) product.

Synthesis of 2-(7,7-dimethyl-7H-fluoreno[4,3-b]benzofuran-1-yl)pyridine

A round flask was charged with2-(7,7-dimethyl-7H-fluoreno[4,3-b]benzofuran-1-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(2.0 g, 4.87 mmol), 2-chloropyridine (0.664 g, 5.85 mmol), Pd₂(dba)₃(0.09 g, 0.098 mmol),dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.16 g,0.39 mmol), K₃PO₄ (3.62 g, 17.06 mmol), 150 mL toluene and 15 mL water.Nitrogen was bubbled through the reaction mixture for 20 mins, and thenthe reaction mixture was heated up to reflux and stirred at refluxovernight. The product was purified using silica gel chromatograph, andwas confirmed by GC. ˜1.3 g product (73.8% yield) was obtained.

Synthesis of Compound 1

A round flask was charged with iridium complex precursor (1.6 g, 2.24mmol), 2-(7,7-dimethyl-7H-fluoreno[4,3-b]benzofuran-1-yl)pyridine (1.3g, 3.59 mmol), 30 mL methanol and 30 mL ethanol. The reaction mixturewas heated up to reflux (oil bath; ˜85° C.) for and stirred at refluxfor 7 days. The reaction mixture was purified using a silica gel column.˜0.82 g (42.5% yield) pure product was isolated, which was confirmed byLC-MS and HPLC.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

The disclosures of each and every patent, patent application, andpublication cited herein are hereby incorporated herein by reference intheir entirety. While this invention has been disclosed with referenceto specific embodiments, it is apparent that other embodiments andvariations of this invention may be devised by others skilled in the artwithout departing from the true spirit and scope of the invention. Theappended claims are intended to be construed to include all suchembodiments and equivalent variations.

We claim:
 1. A compound of Formula II

wherein R has the following structure and is fused to ring A:

Z¹ to Z⁸ is independently selected from nitrogen or carbon; and the wavelines indicate the bonds to two of the adjacent Z¹ to Z⁴ of ring A;wherein when two of the adjacent Z¹ to Z⁴ are used to fuse to R, thosetwo of the adjacent Z¹ to Z⁴ are carbon; R¹ and R⁴ independentlyrepresent mono, di, tri, or tetra substitutions, or no substitution; R²and R³ independently represent mono, or di substitutions, or nosubstitution; R⁷ and R⁸ independently represent mono, di, tri, or tetrasubstitutions, or no substitution; wherein X is O or S; wherein R¹, R²,R³, R⁴, R⁷, and R⁸ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; wherein any two adjacentsubstituents R¹, R², R³, R⁴, R⁷, and R⁸ are optionally joined to form aring, which can be further substituted; wherein R⁵ and R⁶ areindependently branched alkyl which is partially deuterated, or linearalkyl which is partially deuterated; or R⁵ and R⁶ are alkyl and togetherjoin to form a ring which is substituted with hydrogen, deuterium,alkyl, cycloalkyl, or combinations thereof.
 2. The compound of claim 1,wherein each of Z¹ to Z⁴ is carbon.
 3. The compound of claim 1, whereineach of Z⁵ to Z⁸ is carbon.
 4. The compound of claim 1, wherein each ofZ¹ to Z⁸ is carbon.
 5. The compound of claim 1, wherein at least one ofZ⁵ to Z⁸ is nitrogen.
 6. The compound of claim 1, wherein X is O.
 7. Thecompound of claim 1, wherein R⁵ and R⁶ are alkyl and together join toform a ring which is substituted with hydrogen, deuterium, alkyl,cycloalkyl, or combinations thereof.
 8. The compound of claim 1, whereinthe Formula II includes a ligand L_(A) selected from the groupconsisting of:


9. The compound of claim 1, wherein the Formula II includes a ligandL_(B) selected from the group consisting of:


10. The compound of claim 8, wherein the compound has the formulaIr(L_(A))(L_(B))₂; wherein L_(B) is selected from the group consistingof:


11. The compound of claim 1, wherein R⁵ and R⁶ are independentlybranched alkyl which is partially deuterated.
 12. The compound of claim1, wherein R⁵ and R⁶ are independently linear alkyl which is partiallydeuterated.
 13. An organic light emitting device (OLED) comprising: ananode; a cathode; and an organic layer disposed between the anode andthe cathode, the organic layer comprising a compound of Formula II

wherein R has the following structure and is fused to ring A:

Z¹ to Z⁸ is independently selected from nitrogen or carbon; and the wavelines indicate the bonds to two of the adjacent Z¹ to Z⁴ of ring A;wherein when two of the adjacent Z¹ to Z⁴ are used to fuse to R, thosetwo of the adjacent Z¹ to Z⁴ are carbon; R¹ and R⁴ independentlyrepresent mono, di, tri, or tetra substitutions, or no substitution; R²and R³ independently represent mono, or di substitutions, or nosubstitution; R⁷ and R⁸ independently represent mono, di, tri, or tetrasubstitutions, or no substitution; wherein X is O or S; wherein R¹, R²,R³, R⁴, R⁷, and R⁸ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; wherein any two adjacentsubstituents R¹, R², R³, R⁴, R⁷, and R⁸ are optionally joined to form aring, which can be further substituted; wherein R⁵ and R⁶ areindependently branched alkyl which is partially deuterated, or linearalkyl which is partially deuterated; or R⁵ and R⁶ are alkyl and togetherjoin to form a ring which is substituted with hydrogen, deuterium,alkyl, cycloalkyl, or combinations thereof.
 14. The OLED of claim 13,wherein the OLED is incorporated into a device selected from the groupconsisting of a consumer product, an electronic component module, and alighting panel.
 15. The OLED of claim 13, wherein the organic layer isan emissive layer and the compound is an emissive dopant or anon-emissive dopant.
 16. The OLED of claim 13, wherein the organic layerfurther comprises a host; wherein the host comprises a triphenylenecontaining benzo-fused thiophene or benzo-fused furan; wherein anysubstituent in the host is an unfused substituent independently selectedfrom the group consisting of C_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁,N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1),Ar₁, Ar₁-Ar₂, and C_(n)H_(2n)—Ar₁, or the host has no substitution;wherein n is from 1 to 10; and wherein Ar₁ and Ar₂ are independentlyselected from the group consisting of benzene, biphenyl, naphthalene,triphenylene, carbazole, and heteroaromatic analogs thereof.
 17. TheOLED of claim 13, wherein the organic layer further comprises a host,wherein the host comprises at least one chemical group selected from thegroup consisting of triphenylene, carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. 18.The OLED of claim 13, wherein the organic layer further comprises a hostand the host is selected from the group consisting of:

and combinations thereof.
 19. A formulation comprising a compound ofFormula II

wherein R has the following structure and is fused to ring A:

Z¹ to Z⁸ is independently selected from nitrogen or carbon; and the wavelines indicate the bonds to two of the adjacent Z¹ to Z⁴ of ring A;wherein when two of the adjacent Z¹ to Z⁴ are used to fuse to R, thosetwo of the adjacent Z¹ to Z⁴ are carbon; R¹ and R⁴ independentlyrepresent mono, di, tri, or tetra substitutions, or no substitution; R²and R³ independently represent mono, or di substitutions, or nosubstitution; R⁷ and R⁸ independently represent mono, di, tri, or tetrasubstitutions, or no substitution; wherein X is O or S; wherein R¹, R²,R³, R⁴, R⁷, and R⁸ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; wherein any two adjacentsubstituents R¹, R², R³, R⁴, R⁷, and R⁸ are optionally joined to form aring, which can be further substituted; wherein R⁵ and R⁶ areindependently branched alkyl which is partially deuterated, or linearalkyl which is partially deuterated; or R⁵ and R⁶ are alkyl and togetherjoin to form a ring which is substituted with hydrogen, deuterium,alkyl, cycloalkyl, or combinations thereof.